Various compositions prepared by the sulfurization of olefins and olefin-containing compounds are known in the art, as are lubricants containing these products. Typical sulfurized compositions prepared by reacting olefins such as isobutene, diisobutene, and triisobutene with sulfur under various conditions are described in, for example, Chemical Reviews, 65, 237 (1965). Other references describe the reaction of such olefins with hydrogen sulfide to form predominantly mercaptans with sulfides, disulfides and higher polysulfides also being formed as by-products. Reference is made to J. Am. Chem. Soc., 60, 2452 (1938), and U.S. Pat. No. 3,419,614. The patent describes a process for increasing the yield of mercaptan by carrying out the reaction of olefin with hydrogen sulfide and sulfur at a high temperature in the presence of various basic materials.
It also has been known that Diels-Alder adducts can be sulfurized to form sulfur-containing compositions which are particularly useful as extreme pressure and anti-wear additives in various lubricating oils. U.S. Pat. Nos. 3,632,566 and Re. 27,331 describe such sulfurized Diels-Alder adducts and lubricants containing said adducts. In these patents, the ratio of sulfur to Diels-Alder adduct is described as being a molar ratio of from about 0.5:1.0 to 10.0:1.0. The patents indicate that it is normally desirable to incorporate as much stable sulfur into the compound as possible, and therefore, a molar excess of sulfur normally is employed. The disclosed lubricating compositions may contain other additives normally used to improve the properties of lubricating compositions such as dispersants, detergents, extreme pressure agents, and additional oxidation and corrosion-inhibiting agents, etc. For some lubricant applications, however, the above-described sulfur-containing compositions have not been entirely adequate as multi-purpose additives.
Organophosphorus and metal organophosphorus compounds are used extensively in lubricating oils as extreme pressure agents and anti-wear agents. Examples of such compounds include: phosphosulfurized hydrocarbons such as the reaction product of a phosphorus sulfide with turpentine; phosphorus esters including dihydrocarbyl and trihydrocarbyl phosphites; and metal phosphorodithioates such as zinc dialkylphosphorodithioates. Because of the toxicological problems associated with the use of organophosphorus compounds, and particularly with the metal dialkylphosphorodithioates, there is a need to develop lubricant compositions containing low levels of phosphorus, yet characterized as having acceptable oxidation inhibition and anti-wear properties. Lubricants containing low levels of phosphorus also are desirable in view of the tendency of phosphorus to poison catalytic converters used to control emissions from gasoline engines.
Polyvalent metal salts of dithiocarbamic acids are known and have been described as being useful oil additives because they serve the dual function of sequestering undesirable metal components of the oil and because they function as anti-oxidants. Lubricating oil compositions have been described comprising combinations of various polyvalent metal dithiocarbamates with other chemical additives exhibiting desirable property-improving characteristics when added to the lubricating oil in combination with the dithiocarbamates. For example, U.S. Pat. No. 2,999,813 describes a lubricating composition comprising a sulfurized mineral oil and a polyvalent metal dithiocarbamate. Preferably, the composition also includes a lead soap of a naphthenic fatty acid. The preparation of lubricating compositions comprising mineral oil, metal salts of dithiocarbamic acids and coupling agents such as alcohols, esters, ketones and other stable oxygen-containing materials is described in U.S. Pat. No. 2,265,851. U.S. Pat. No. 2,394,536 describes lubricating oil compositions containing the combination of organic sulfides and salts of dithiocarbamic acids. Organic sulfides generally are represented by the formula R.sub.1 (S).sub.n R.sub.2 wherein R.sub.1 and R.sub.2 are aliphatic groups and n is 1, 2 or 3.
U.S. Pat. No. 2,805,996 describes the use of amine-dithiocarbamate complexes in lubricating oil compositions, and U.S. Pat. No. 2,947,695 describes the advantages of utilizing mixtures of polyvalent metal dithiocarbamates in preparing oil-soluble additive compositions useful in the preparation of lubricating oils.